Thermal Analysis of Plug-in Hybrid Vehicle Batteries in Car Carrier Cargo Holds: Implications for Mitigating Fire Risk

Abstract

Concerns have arisen over the potential for fires in electric cars (EVs) during maritime transport, particularly following recent incidents involving car carrier fires. The aim of this study is to provide a clearer picture of the environmental conditions that affect electric vehicles during transport at sea and to provide insight on how to improve maritime practises related to fire risks from battery thermal runaway.

This study examines the thermal behaviour of Plug-In Hybrid electric vehicles (PHEV) batteries during a one-month voyage on a car carrier. Temperature data from 95 PHEVs distributed across two decks (one near the vessel's fuel tanks and one nearer to the superstructure) were analysed to investigate potential correlations among the temperatures of the sea, outside air, ambient hold, and fuel tank surface.

The research shows that PHEV battery temperatures correlate with sea, air, ambient hold, and fuel tank surface temperatures to various degrees, with notable spatial variability across the vessel. Sea temperature effects are most prominent near the starboard side, while passive ventilation on the port side creates localized cooling microclimate with negative correlations. On upper decks, outside air and ambient hold temperatures show strong correlations, especially where direct sunlight exposure and limited airflow create warmer zones, though anomalies under ventilation hatches show the existence of microclimates within. Proximity to heated fuel tanks on lower decks increase PHEV battery temperatures, confirming their impact, but there is a need for more detailed monitoring and localized analysis.

The correlation analysis indicates that PHEV battery temperatures are strongly influenced by environmental factors. Spatial variability across decks shows that localized conditions—such as proximity to heat sources and passive ventilation—play a big role in potential battery heat buildup. Current stowage practices are inadequate for PHEVs, as they lack identification standards, temperature monitoring records, and data collection. The author calls for revised protocols including ventilation-aware placement, vertical separation of EVs, and sharing temperature data among vehicle carriers for a data-base build up.